1. Field of the Invention
The present invention relates to a dynamoelectric machine such as an automotive alternator, for example, and particularly to a brush assembly construction for a dynamoelectric machine and a method for mounting a brush assembly to a brush holder enabling improved mounting of the brush assembly.
2. Description of the Related Art
Generally, a brush holding apparatus in a dynamoelectric machine such as an automotive alternator, for example, is mounted internally in a tightly-closed case, making it is necessary to dismantle the case during brush replacement, thereby making workability extremely poor.
Thus, an automotive alternator in which an opening is disposed in a portion of the case facing the brush holding apparatus, enabling the brushes to be changed through the opening, has been proposed in Japanese Patent Laid-Open No. SHO 51-66409 (Gazette), etc., for example.
FIGS. 27 and 28 are a partial longitudinal section and a plan, respectively, showing a vicinity of the brush holding apparatus of the conventional automotive alternator described in Japanese Patent Laid-Open No. SHO 51-66409, for example, and FIG. 29 is a perspective showing a brush assembly used in the brush holding apparatus shown in FIGS. 27 and 28.
In FIGS. 27 to 29, a rotor 81 is fixed to a shaft 82 rotatably supported in a front bracket (not shown) and a rear bracket 84a by means of bearings 83, being disposed inside a case 84 composed of the front bracket and the rear bracket 84a. Slip rings 85 are mounted to a rear-end end portion of the shaft 82.
A stator 86 is constituted by: a cylindrical stator core 87; and a stator winding 88 installed in the stator core 87, first and second end portions of the stator core 87 being held between the front bracket and the rear bracket 84a, the stator 86 being disposed so as to surround the rotor 81.
A brush holding apparatus 89 is constituted by: a brush body portion 90 through which a pair of brush-housing angular apertures 90a are disposed; and a pair of brush assemblies 95 in each of which a brush 91, a pigtail 92, a brush spring 93, and a brush terminal 94 are assembled integrally. This brush holding apparatus 89 is mounted to the rear bracket 84a by securely fastening the brush body portion 90 to an inner wall surface of an end portion of the rear bracket 84a by means of a bracket screw 96, inserting the brushes 91 of each of the brush assemblies 95 into the brush-housing angular apertures 90a, and securely fastening the brush terminals 94 to the brush body portion 90 by means of terminal screws 97. Thus, the brushes 91 are forced into contact with the slip rings 85 by the brush springs 93.
In addition, an opening 98 for brush replacement is disposed through a portion of a side wall of the rear bracket 84a facing the brush body portion 90. A cover 99 is securely fastened to an outer circumferential surface of the side wall of the rear bracket 84a by means of cover screws 100 so as to cover the opening 98.
A brush replacement operation for the conventional automotive alternator constructed in this manner will now be explained.
First, the cover 99 is removed by removing the cover screws 100. Then, the terminal screws 97 are removed and the brush assemblies 95 are pulled out through the opening 98. Next, the brushes 91 of new brush assemblies 95 are inserted into the brush-housing angular apertures 90a, and the brush terminals 94 are pressed toward the slip rings 85 until the brush terminals 94 are placed in contact with mounting terminals 90b on the brush body portion 90. At this time, the brush springs 93 are compressed, and the pigtails 92 are housed inside the brush springs 93 in a flexed state and become entangled. Then, the brush terminals 94 are securely fastened to the mounting terminals 90b of the brush body portion 90 by means of the terminal screws 97 while pressing the brush springs 93. In addition, the cover 99 is placed over the opening 98 and securely fastened to the rear bracket 84a by means of the cover screws 100, completing replacement of the brushes 91.
In the conventional automotive alternator, the brush assemblies 95 are each assembled by passing a pigtail 92 having a first end joined to a brush 91 through a brush spring 93 formed into a coil shape and joining a second end of the pigtail 92 to a brush terminal 94 with the brush spring 93 in a compressed state. Thus, because the brush springs 93 are not restricted at all relative to a direction of bending, the flexed portions of the pigtails 92 may be pinched by the brush springs 93 or may apply bending stress to the brush springs 93 during the process of pressing the brush terminals 94 after inserting the brushes 91 into the brush-housing angular apertures 90a, giving rise to bending of the brush springs 93. In addition, because there are no members to guide the brush springs 93 as they are being compressed, if the balance of the pressure acting on the brush springs 93 becomes uneven, the brush springs 93 may become bent.
Consequently, because portions of the brush springs 93 projecting out of the brush-housing angular apertures 90a bend and flop over in the process of pressing the brush terminals 94, one problem has been that workability when mounting the brush assemblies 95 to the brush body portion 90 has been poor.